The subject matter of the instant invention relates to compositions and methods used for making foam; particularly polyurethane foam.
Flexible molded foams are conveniently produced using tertiary amine compounds that can catalyze the reaction between water and isocyanate (blowing reaction) and between alcohol and isocyanate (gelling reaction). In some particular cases where molded foam parts are produced, delay action catalysts can be more conveniently used because they provide the advantage of slower reactivity during the pouring process. These catalysts are composed of a tertiary amine that have been reacted (or blocked) with an organic acid. As heat is evolved during the polymerization reaction, dissociation of the tertiary amine salts to the tertiary amine catalysts and acid can occur thereby causing the foam to cure. Foam produced in this manner is normally characterized by the presence of a relatively high percentage of closed polyurethane cells causing the foam to shrink when cooling due to its poor dimensional stability.
In order to maintain the dimensional stability the catalysts or acid blocked catalysts were combined with cell openers in an aqueous system. U.S. Pat. No. 6,136,876 and U.S. Pat. No. 6,248,801 discloses a method for making polyurethane foam in which a polyisocyanate is reacted with a polyol in the presence of a urethane catalyst, a blowing agent, optionally a silicon surfactant cell stabilizer and a cell opening additive. The cell opening additive comprises a substance containing an active methylene or methine group. The cell opener can be delivered as a neat liquid or dissolved in one of the components of the formulation such as the surfactant, water, crosslinker, polyol, amine catalyst or catalysts. One example of cell opener containing active methylenic groups is 2-cyanoacetamide. The main disadvantages of dispensing 2-cyanoacetamide in the polyol, crosslinker, surfactant, amine catalyst or catalysts or mixtures of any of the components used in the formulation is the no solubility or negligible solubility of 2-cyanoacetamide. Some amine catalysts or crosslinkers can even react with 2-cyanoacetamide causing the release of ammonia or the formation of colored products. Water could be used as the sole solvent to dispense 2-cyanoacetamide in a polyurethane formulation. However there are a few disadvantages when using water as solvent including: a) poor solubility; b) reduced the cell opening efficiency (requiring higher use level of cell opener); c) foam shrinkage, and; d) poor reproducibility. Other conventional chemical methods for controlling foam shrinkage have drawbacks such as requiring high levels of cell opener (often as high as 1-5 pphp) and/or adversely affecting the physical properties of foam and/or using environmentally undesirable substances and/or using materials that are very difficult to dispense in a liquid form to a polyurethane foam system.
Shrinkage of flexible molded polyurethane foam may also be controlled by using mechanical crushing to open foam cells and improve dimensional stability of foam. Current mechanical methods for cell opening consist mainly of crushing, vacuum rupture or time pressure release.
Upon demolding of a foam article mechanical crushing and breaking of polyurethane foam cells enables the foam to be more dimensionally stable. Another method of breaking foam cells is vacuum-crushing which involves drawing a vacuum on the finished polyurethane product inducing cell rupture. The overall effect of these methods is reduced foam shrinkage.
Other mechanical methods have been used to achieve dimensionally stable foam, such as decreasing cycle production times. For example, demolding the polyurethane foam in three minutes as compare to four minutes will dramatically improve the dimensional stability. Another method for producing dimensionally stable foams is time pressure release (TPR). TPR comprises opening the mold during process to release the internal pressure and then reclosing for the duration of the cure time. The sudden release of internal pressure burst the cell windows, thereby obtaining dimensionally stable foam products.
Mechanical methods usually result in incomplete or inconsistent cell opening and require flexible molded foam producers to invest in additional machinery.
U.S. Pat. No. 3,314,834 discloses diketo compounds form effective potlife extension agents in polyurethane propellants.
U.S. Pat. No. 3,635,906 discloses that certain chelate-forming compounds have the effect of delaying initiation reaction between an organic polyisocyanate and an organic polyhydroxy compound in the presence of an amine free organotin cure rate catalyst.
U.S. Pat. No. 4,426,510 discloses coating or adhesive compositions having extended potlife and short cure time comprising an organic polyol, an organic polyisocyanate, an organozinc cure rate catalyst, and a compound selected form a) beta-dicarbonyl compounds, b) alpha-hydroxy ketones, c) fused aromatic beta-hydroxy ketones and d) beta hydroxyl nitrogen-heterocyclic fused aromatics.
GB 2303372 discloses making polyurethane foams using the mechanical frothing technique and a catalyst system comprising a metal acetyl acetonate and acetyl acetone.
U.S. Pat. No. 4,721,642 discloses a blocked polyisocyanate prepolymer formed by blocking the terminal —NCO group of the polyisocyanate with a blocking agent such as alcohol, phenol, ethyl acetoacetate, e-caprolactam, MEK oxime, diethyl malonate, acetyl acetone, cyanic acid and sodium bisulfite. A polyurethane resin foamable paint comprises an aqueous dispersion composed of blocked polyisocyante prepolymer, additives, chain extender, foaming agent and emulsifier.
CA 2141890 discloses the production of rigid polyurethane, polyisocyanurate and polyurethane urea foams with HCFC blowing agents and optionally a flame retardant and/or chelating agent which is acidic, i.e., having a pKa value from 0 to 10.
U.S. Pat. No. 3,972,846 discloses a curable polyurethane composition comprising a keto compound and a liquid mixture of an organic aliphatic polyfunctional polyisocyanate and a compound having active hydrogen.
U.S. Pat. No. 4,251,635 discloses flexible polyurethane foams having reduced tendency to form burning embers when it is ignited and burned by incorporating a ketone or benzaldehyde into the reaction mixture before foaming.
DE 1 005 722 discloses that reaction of polyols with polyisocyanates can be retarded by adding an imine (the condensation product of a primary amine and an aldehyde or a ketone or a diketone).
DE 2 451 726 discloses a process for slowing down the reaction of isocyanates compounds with polyester polyols in which the polyols contain at least one aldehyde and/or ketone and a mono-amine in the molar ratio of aldehyde or ketone group:amino group from 1:0.1 to 1.
U.S. Pat. No. 6,136,876 discloses a method for preparing flexible polyurethane foam by reacting an organic polyisocyanate with a polyol in the presence of urethane catalyst, water as blowing agent, optionally a silicon surfactant, and a cell opener characterize in that the cell opener comprises an active methylene or methine group containing compound.
U.S. Pat. No. 6,248,801 discloses a method for preparing flexible polyurethane foam by contacting an organic polyisocyanate with a polyol in the presence of urethane catalyst, water as blowing agent, optionally a silicon surfactant cell stabilizer, and a cell opening additive. The cell opening additive comprises an active methylene or methine compound which also contains a tertiary amine.
The disclosure of the previously identified patents and patent applications is hereby incorporated by reference.